Download Strategizing Power Utilization within Intelligent Tags

International Journal of P2P Network Trends and Technology (IJPTT) – Volume 9 – June 2014
Strategizing Power Utilization within Intelligent
Tags
Dr. JKR Sastry1, and Dr. A. Vinya Babu2
1
Department of Computer Science and Engineering, KL University
Department of Computer Science and Engineering, JNTU Hyderabad
2
Abstract: Power management within intelligent Tags is one of the
most important issues that must be given with utmost importance
as the Tags are driven by battery power and the longevity of the
battery must be increased so as to reduce the requirement of
reducing frequency of charging or replacing the battery.
Intelligent tags have many built-in functions that are required
for supporting many of the intelligent issues such as
identification, locating the tags etc. Each built-in intelligence
requires certain amount of power. An event taking place either
internally or externally involves usage of a set of intelligent
modules which all adds to the requirement of certain amount of
power. Power management has a direct impact on the latency
with which the intelligent functions can be supported. This paper
presents some of the strategies for power saving when a set of
relevant functions are to be activated keeping in view of power
and latency reduction.
Keywords: Power reduction, PSM, CAM, Latency reduction,
Intelligent Tag, power saving, Conserving battery discharge,
battery saving, battery recharging
I. INTRODUCTION
Power consumption is one of the limiting factors for any
embedded device mainly of those which are battery driven. As
the technology advances, the size of the mobile embedded
device is minimized for the easy use. So, the size of the
battery is being reduced along with other components to
reduce the overall size of the embedded device. But, the
reduction of size leads to reduction of total charge retained by
the battery thereby decreasing its life time. The frequent
charging and recharging of the battery is not performed
especially when the devices in which the battery is fitted are
mobile. However if we succeed in reducing the overall power
consumed by the components in the device, the luxury of
either reducing the battery size while retaining the original
characteristics or increasing the battery lifetime while
retaining the original size or combination of both can be
achieved.
The power consumption in the embedded device depends on
the power required and consumed by the various components
in it. The battery lifetime can be prolonged by decreasing the
power consumed by the components. Several available power
management techniques provide the required power reduction
in embedded devices. Battery charge can be preserved through
various methods like allowing the central processing unit
(CPU) to slow down, suspend or shut down part or all of the
system. Tags generally consist of many modules which are
integrated. Not all the modules will be active all the time. The
unused modules can be shut-down or sent to sleep mode.
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Different challenges like software optimization, low power
communication, low power display and low power data
management and fault tolerance should be considered to
increase the longevity of the battery.
Power management policies can be described at various levels
of abstraction starting from the lowest level transistor to the
final application level. The different levels of abstraction
include transistor level, architectural level, system level and
the application level. The application is usually responsible
for the power management as the power consumed depends
on various running states of the components of application.
Power is required for driving any of the hardware. The
embedded software can be used to analyze and improve the
power characteristics of the system. Real time operating
system (RTOS) generally provides system functions with
which the power availability to various parts of the systems
can be managed. The user application will be able to
recognize the current battery status by invoking related
functions supported by RTOS. Once the power requirements
of the components are known, the user application should be
able to bring the requirement of the power to the lowest level.
The system should be able to perform the required operation
without losing its efficiency. The efficient power states can be
achieved by allowing several components or the combination
of the components to be inactive or in sleep mode when the
same are not required functionally.
Power management does not reduce the performance of the
system but simply add features to reduce the power
consumption. The low power or sleep modes helps to prolong
the life of batteries. Disabling power to one device should not
affect any other device. Displays in mobile devices can be
power managed by dimming or blanking of displays by
cutting power to those devices in idle mode. Device entering
to low power mode is generally controlled by timers and
switching back to full power mode is done by triggering
which is either done manually or automatic.
Power is required to drive the hardware and execute software.
The most important areas of an Embedded System
implementation that are quite related to more power
consumption include areas such as
display, wireless
peripherals, code execution and memory. It is necessary to
provide the mechanisms to determine the power requirements
of the components in the system and to provide the power
management techniques to manage the overall power of the
system to the lowest level thereby increasing the life of the
battery.
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International Journal of P2P Network Trends and Technology (IJPTT) – Volume 9 – June 2014
Intelligence has to be added for efficient power management
within the Tags. The addition of intelligence to the Tags is
important from the point of view of longevity of battery as
much as possible considering that the intelligent Tags are
remotely situated and that the intelligent TAG must support
many number of functional modules which works in
conjunction with embedded hardware.
used can be placed in low power states. This reduces the
power consumption. The relationship and interactions
between system, application and device power managers with
each other using UML class diagrams, sequence diagrams and
state charts are proposed. This object oriented approach make
the embedded system more efficient, easy to maintain and
faster to develop.
Following are some of the major issues that affect the
power of the TAG.
A power management system [3] has been included into
cinder operating system. The feature that is related to
controlling power through proper allocation is useful and
important to be included into the operating systems that are
used in mobile devices. A reserve is a mechanism for resource
delegation, providing fine-grained accounting and acting as an
allotment from which applications draw resources. “Cinder”
estimates energy consumption using standard device-level
accounting and modeling. Their research findings have been
proposed which includes an operating system that implements
“reserves and taps” as new mechanisms for managing and
controlling energy consumption, evaluating the effectiveness
and power of these mechanisms in a variety of realistic and
complex application scenarios running on a real mobile phone
and experiences in writing a mobile phone operating system,
outlining the challenges and impediments faced when
conducting systems research on the dominant end-user
computing platform.

Choice of appropriate power management system
that help lowering the power of a TAG when several
modules are integrated in the TAG.

A TAG with high longevity of the battery.

Implementing
challenges
like
low
communication, low power display etc.

To manage power without losing efficiency of an
embedded systems.
power
Thus the problem is to determine the power requirements of
the components in the system and to determine various power
reduction strategies and power management techniques to
manage the overall power of the system to the lowest level
thereby increasing the life of the battery while at the same
time maintaining efficiency.
II. RELATED WORK
An enhanced RFID technology [1] provides various
functionalities like high operating range and sensing and
monitoring capabilities. These functionalities require data
acquisition units, real time clocks and active transmitters
which in turn cause a high power consumption of the TAG.
Several power management techniques for battery driven Tags
supported by energy harvesting devices are proposed. Sleep
transition protocol and wakeup control protocol is the power
saving strategy where system is in power saving state as long
as possible. The TAG stays in sleep mode and shifts to the
active mode when triggered by a certain event. The additional
power can be provided by energy harvesting devices which
converts the energy from environment into electrical energy.
The lifetime of the battery can be increased. The common
energy sources are mechanical energy (vibrations-piezo
generator), solar light (solar cells), thermal energy (thermo
generator) and some less common sources like
electromagnetic energy. This generated power requires special
storage and buffer structures. The two types of storage devices
are primary storage and secondary storage. The primary
devices are not rechargeable and secondary devices are
rechargeable.
An abstract model of a system power manager (PM), device
power manager and application power managers has been
proposed [2]. Power management in embedded devices can be
developed for real time operating systems or its applications.
If power management techniques are present in embedded
devices, the features and components which are not being
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WLAN power conservation technologies have been in use
these days [4].. The power save mode is just one of a range of
options. Constantly awake (CAM) is one of the techniques
which are widely used today where the power saving features
is disabled due to reduction in performance in terms of
throughput when power saving measures is enabled. Power
save mode (PSM) is the method in which the mobile device is
switched off after a prefixed length of time. The device is
wakeup periodically for any data. Unscheduled automatic
power save delivery (U-APSD) is the method where the client
is allowed to access the data without waiting for the next
beacon. This technique is efficient in case of lighter traffic
loads. Power save multi poll (PSMP) is used for multiple
radios. The WI-FI adapter intimates the access point that it
was powered down. The access stores the data received by it
and returns it to the adapter only when it is turned on again.
However it increases latency and traffic when it is turned on.
Wi-Fi power saving mode radios consumes power for both
transmitting and receiving [5]. A typical laptop Wi-Fi radio
may consume a few watts while in use. There are several
tricks and tweaks you can perform to reduce the power
consumption, even when you are using Wi-Fi all the time.
Because of the power requirements for Wi-Fi, the Power Save
Poll protocol (PS-Poll) was developed to help reduce the
amount of time a radio needs to be powered. Rather than
having the radio all the time, PS-Poll allows the Wi-Fi adapter
to notify the access point when it will be powered down.
While the radio is powered down, the access point will hold
any network packets which would need to be sent to it. Of
course, the longer the radio is off, the more power you save.
Device Drivers can control time elapses before the radio is
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International Journal of P2P Network Trends and Technology (IJPTT) – Volume 9 – June 2014
turned on again, to get the pending packets from the access
point.
Conservation of battery power is important for low TAG
maintenance [6]. The energy saving mechanism on the active
Tags is proposed which is referred as smart buffer. It consists
of circuit fabricated in silicon that looks at the destination of
each packet of ISO standard and produces a wake up signal.
The smart buffer requires considerably less power than is
required by the TAG to interrogate the same message to
determine the target destination. This invention presents a
model tracking the energy used by a set of Tags. It provides a
basis to investigate and determine the conditions that must be
met for the smart buffer equipped TAG to produce a net
energy savings.
Software level methods for optimizing the power in wireless
embedded devices have been proposed [7[. Power
consumption in wireless devices is an important concern in
such devices. Power optimization can be done either by
changes in hardware or software. Generally hardware is fixed
by the vendor and cannot be modified by the user. The
software level changes can be performed by the user
according to the requirements. The loop optimization methods
were used and tested to reduce the power consumption to
some extent. Similarly unrolling and loop alignment were
used to increase the performance in terms of power. The
software level methods like nested switches, no of parameters,
no of local variables, data type are proposed which improves
the power consumption of the coding.
Power management technique for location estimation have
been proposed [8]. The algorithm is used in two forms. One
form is used to locate to locate a device in a single and when
the device falls at the intersection of two or more terrains.
Location of the handheld device is used as a parameter for
cluster calculation. The location estimation is done by
triangulation method. The algorithm uses the information
about the terrain obtained through google maps. The
information is subjected to Signal to Noise Ratio (SNR),
phenomenon of reflection, diffraction and scattering and the
power required by the portable device for effecting the
communication with the tower is calculated. Calculation of
the location is based on the available signal strength (ASS)
and the receive signal strength (RSS). They have considered
GSM architecture and the cell phone for operating as a
portable device. The algorithm takes into account that when a
device is not participating in the communication, it is directed
to change its state from the active mode to a park mode, so the
device will save the battery power. Proposed technique falls in
the Dynamic Power Management (DPM) category as it is
dealing with the battery power during run time.
Power optimization for secured Bluetooth based
communication has been proposed [9]. Bluetooth technology
is capable of providing many services like high data
throughput, adhoc networks providing excellent data
transmission and many other services in various applications.
Power consumption is high compared to other mobile devices
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due to continuous monitoring. As the device is small and high
throughput, there is a need for power optimized algorithm
which allows high throughput with less power consumption.
The power consumption in Bluetooth can be reduced to a
certain level using four operational modes. They are active,
sniff, hold and park modes. The battery lifetime can be
increased through these modes.
[10] proposed a power management technique for location
estimation. Power management techniques in embedded
devices can be developed as a part of real time operating
systems or its applications. If power management techniques
are present in embedded devices, the features and components
which are not being used can be placed in low power states.
This reduces the power consumption. While a device is not
participating in the communication, it is directed to change its
state from the active mode to a park mode, so the device will
save the battery power. The technique recommended by them
falls in the category of Dynamic Power Management (DPM)
as it is dealing with the battery power during run time.
Dynamic voltage scaling (DVS) [11] is one of the techniques
in reducing the power dissipation by lowering the supply
voltage and operating frequency. Real-time DVS algorithms
are presented to provide power savings while maintaining
real-time issues. Power consumption in Bluetooth is high
compared to other mobile devices due to continuous
monitoring. As the device is small and need to support high
throughput, there is a need for power optimization which
allows for high throughput with less power consumption.
Different challenges such as, software optimization, low
power communication, low power display and low power data
management and fault tolerance in addition to other saving
techniques using which the longevity of the battery could be
increased have been addressed [12]. A combination of
techniques has been used in the intelligent TAG to increase
longevity of the battery. Dynamic voltage and frequency
scaling (DVFS), Dynamic power management, utilization of
various powers saving modes, usage of various power saving
protocols etc. The combination of various power management
techniques provide an efficient mechanism to reduce the
overall power consumption of the intelligent TAG. A software
architecture for development of an embedded application
which helps in conserving the power consumption and
extending the longevity of the battery has been presented [13].
III. POWER MANAGEMENT STRATEGIES
Power is required for processors, peripheral devices, and
Built-in devices within the micro controller. The micro
controllers are designed to operating in various power saving
modes which include switching the power to micro controller
and restarting the microprocessor using a restart mechanism,
switching the power to microprocessor and switching on the
power to the microprocessor and switching on the power
when an interrupt is initiated by the peripheral and switch on
and off the power to the peripherals by the user application. In
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International Journal of P2P Network Trends and Technology (IJPTT) – Volume 9 – June 2014
the case intelligent systems power to the micro controller is
not switched off. The method of switching on and off the
power to the peripheral can be controlled through the power
management system (PMS) which is one of the modules to be
inbuilt into the intelligent Tag. The PMS will switch on the
power to peripheral device when its related interrupt has been
received by the microcontroller. The I/O is undertaken after
the I/O device is powered on and the power to the peripheral
device is switched off after the it’s related I/O is completed.
Intelligent Tags have to communicate with the remote mobile
devices continuously in communicate with it every time
information related to identification, change of location,
tampering, power depletion taking place below the safety
levels using with Wi-Fi or Bluetooth interface. The use of
either Wi-Fi or Bluetooth is arbitrated as when the restart of
the intelligent tag takes place and based on the arbitration
results one of the communication device is chosen and the
power to the other deice is switched off. Constant awake
protocols are to be used to keep the make the chosen
communication device awake.
The response time required in case of each of the event taking
place in relation to an intelligent feature is different. The
identification and change of location can be communicated at
higher level of latency whereas the communication related to
Power depletion, tampering, alerting must be undertaken with
least latency so that the required corrective action is
undertaken with no damage caused to the intelligent system.
The latency is however is dependent on the way an application
system is designed considering the interrupt routine and the
way the signaling is to the concerned tasks is implemented.
frequency can be changed dynamically by implements the
dynamic frequency management system (DFS). The CAM
protocol can also decide the powering on or offing the
communication devices based on whether there is anything
that must be communicated which is actually dependent on
the type of event taking place.
The various strategies that can be adapted and their related
latencies that can be achieved are shown in the Table I. a
combination of strategies that can be applied can be
predefined relating to implementation of a particular
intelligence issue and the same can be implemented through a
power management system (PMS) which works as an
additional module within the embedded system.
The mapping of power management strategies to different
intelligent issues has also been shown in Table I. The power
management system can select one of these strategies based
on the events that take place at any point in time.
IV. EXPERIMENTATION
The proposed system for tag power management is
implemented through embedded C under integrated KEIL
development tool kit. Figure I demonstrate that Bluetooth and
GPS are interfaced to UART0 and UART1 respectively.
Initially the processor and the peripherals will be in sleep
mode.
A different storage can also be implemented that implements
the reduction in power supplied to the peripheral devices
which are connected with the events that can be processed at
acceptable high level latencies. The devices that are related to
intelligent issues that can be undertaken at acceptable high
level latencies can be fed with suitable low level voltages and
the devices that are related to intelligent issues that are to be
undertaken at low level acceptable latencies are to be fed with
high level voltages. The system of dynamically controlling the
power supply to peripheral devices is called as Dynamic
voltage management system (DVS).
The power to be fed to wireless communication devices is also
dependent on the distances to which communication must be
undertaken with the hand held device. The constantly awake
protocol (CAM) determines the distances to which
communication must be undertaken and therefore fixes the
frequency required for effecting the communication. The
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Figure I: Experimental Setup for Power Management
The sleep mode of the tag is notified to the local user through
LCD and remote HOST through message displayed on mobile
as shown in the figure II.
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International Journal of P2P Network Trends and Technology (IJPTT) – Volume 9 – June 2014
V. CONCLUSIONS
Power management in intelligent TAG is one of the important
issues as different technologies must be integrated efficiently
with minimum power consumption to increase the longevity
of the battery. Intelligent Tags must be in communication
with the HOST by using any of the protocols that are
supported on the TAG and the HOST.
Figure II: Message "Sleep Mode" displayed on LCD and
mobile phone
Upon occurrence of any event a power management strategy
is decided and devices that are required to process the event
are made to be in active mode. The power status of the tag is
displayed on LCD and is notified to the HOST through
message as shown in figure III.
The power characteristics of a device are very much
dependent on the type of communication standard used for
effecting the communication. Selection of a particular
communication method has a definite bearing on the power
consumption of the device. Several power reduction
mechanisms have been presented that are suitable for
powering a combination of circuits related to a set of features
that are needed to be supported at a time.
REFERENCES
[1].
[2].
[3].
[4].
[5].
[6].
[7].
[8].
Figure III: Message "Normal Mode" Displayed on LCD
and Mobile Phone
[9].
The power consumptions by various devices from time to time
have been recorded as they are displayed on the LCD and the
messages that have been transmitted to the remote HOST also
have been displayed on the LCD and the same are recorded.
The rate of discharge of battery is decreasing as the time of
usage of the TAG is increasing. This is because of efficient
power management of the devices and routing every operation
to the devices through power management module. The
experimental results as recorded are shown in the Table II. It
can be seen form the table that a saving of more than 50% in
power consumption is achieved by adapting proper power
saving strategy and thereby increasing the life of the battery to
double the time. The actual saving however be dependent on
the frequency of occurrence of the individual events of
different types.
[10].
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[11].
[12].
[13].
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International Journal of P2P Network Trends and Technology (IJPTT) – Volume 9 – June 2014
5.
6.
7.
Alerting
4.
Power
depletion
3.
Tampering
2.
Location
identification
Power Saving Mode (Power of I/O devices
and power on the I/O devices when the
Interrupt from the peripheral device is
received
Dynamic power Management (DVS) through
High voltage regulation
Dynamic power Management (DVS) through
low voltage regulation
Dynamic power Management (DFS) through
High Frequency regulation
Dynamic power Management (DFS) through
low frequency regulation
Implementing constant awake protocol
(powering on and off the wireless
communication devices
Task Prioritization
Tag
identification
Power
Management
strategy
1.
Influencing
Latency
Power Saving
strategy serial
Table I.
Power Saving Strategies
√
√
X
X
X
X
X
√
√
√
√
√
X
X
X
X
X
√
√
√
√
√
X
X
X
√ HIGH
√
HIGH
√ LOW
√
LOW
√
LOW
√ HIGH
√
HIGH
√ LOW
√
LOW
√
LOW
High
Low
HIGH
Low
HIGH
Low/High/
Average
Low/High/
Average
Table II:
Experimental Results for Power Management in Intelligent Tag
Power Consumed in Millie Watts
Event
Total
power
consumed
In
Mille
Watts
Total
power
required if
all
the
devices
are
working
in Millie
watts
Saving in
power
In Millie
watts
ARM7
Wi-Fi
Bluetooth
GPS
Pressure
Sensor
Beeper
Identification
2.400
1.440
0.000
0.000
0.000
0.240
6.240
11.619
5.379
Location
Indemnification
2.328
0.0
0.717
2.156
0.000
0.237
5.438
11.619
6.181
Tampering
2.302
1.421
0.000
0.00
0.235
0.234
4.190
11.619
7.429
Alerting
2.209
1.417
0.000
2.138
0.233
0.232
6.229
11.619
5.319
Power depletion
2.195
0.00
0.702
0.00
0.00
0.230
3.127
11.619
8.419
25.224
58.095
32.817
Total
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